Isolated guinea pig seminal vesicle, comprising homogeneous columnar epithelial cells is used as target tissue to study the mechanism of action of the androgen hormones (testosterone, dihydrotestosterone and 3 alpha-androstanediol). Nuclear events are of prime interest. The nucleus is fractionated into nuclear envelope, nucleosomes and certain insoluble acidic-protein fractions. The sub-nuclear fractions are characterized when possible with respect to enzymatic activities. Independently, the sub-nuclear fractions are evaluated for their ability to bind steroid-receptor complexes. A major goal is to determine if binding is followed by alterations in structure and function.